Duplication of uniqid in PHP with high concurrency

The most recent project has been useful to generate token validation issues. First consider using PHP's uniqid () function to generate a random string, but since the function seems to be based on the microsecond time level. In the case of high concurrency, it is possible to generate the same value.

Solution 1:uniqid (rand (1,10000)), the first parameter of the function can be used as a prefix for the number of builds, thus greatly reducing the repetition rate of the build number. But the possibility of repetition is still there.

Solution 2:md5 (Uniqid ()), use the MD5 () function to generate an absolutely unique value